Is this rude?

Do you think this is rude?

My daughter (turning 4) is having her birthday party in a few days. This morning, 4 days before the party (and the invites were sent out a month ago), one of the moms of another kid in my daughter’s class messages me that her daughter can no longer come because one of her older kids has a sports playoff game.

The party is at a kids party place and since it’s 4 days before I have already given a final count and have ordered favors and supplies based on the number of kids (as well as food for the adults). It’s not like I’m out a significant amount of $, but I feel like this is extremely rude as the party is only a few days away. She RSVPed that she was coming over a month ago.

I think I also feel offended as nowhere in her message did she apologize or even acknowledge that it’s rude to cancel so close to the party.

What do you think, rude or understandable?